U.S. patent application number 14/500541 was filed with the patent office on 2016-03-31 for pin fin compliant heat sink with enhanced flexibility.
The applicant listed for this patent is INTERNATIONAL BUSINESS MACHINES CORPORATION. Invention is credited to Mark D. Schultz.
Application Number | 20160091260 14/500541 |
Document ID | / |
Family ID | 55584018 |
Filed Date | 2016-03-31 |
United States Patent
Application |
20160091260 |
Kind Code |
A1 |
Schultz; Mark D. |
March 31, 2016 |
PIN FIN COMPLIANT HEAT SINK WITH ENHANCED FLEXIBILITY
Abstract
Heat sinks and methods of using the same include a top and
bottom plate, at least one of which has a plurality of pin contacts
flexibly connected to one another, where the plurality of pin
contacts have vertical and lateral flexibility with respect to one
another; and pin slice layers, each having multiple pin slices,
arranged vertically between the top and bottom plates such that the
plurality of pin slices form substantially vertical pins connecting
the top and bottom plates.
Inventors: |
Schultz; Mark D.; (Ossining,
NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
INTERNATIONAL BUSINESS MACHINES CORPORATION |
Armonk |
NY |
US |
|
|
Family ID: |
55584018 |
Appl. No.: |
14/500541 |
Filed: |
September 29, 2014 |
Current U.S.
Class: |
165/185 ;
29/890.03 |
Current CPC
Class: |
F28F 3/022 20130101;
B23P 15/26 20130101 |
International
Class: |
F28F 3/02 20060101
F28F003/02; B23P 15/26 20060101 B23P015/26 |
Goverment Interests
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0001] This invention was made with Government support under
Contract No.: DE-EE0002894 (Department of Energy (DOE)). The
Government has certain rights to this invention.
Claims
1. A heat sink, comprising: a top and bottom plate, at least one of
which comprises a plurality of pin contacts flexibly connected to
one another, wherein the plurality of pin contacts have vertical
and lateral flexibility with respect to one another; and a
plurality of substantially vertical pins connecting the top and
bottom plates.
2. The heat sink of claim 1, wherein at least one of the top and
bottom plates is a corrugated plate that includes interlocking
protrusions on opposite sides of the plate and wherein the pin
contacts are flexibly connected to one another by the top and
bottom plates and wherein the vertical pins comprise a plurality of
pin slice layers, each comprising a plurality of pin slices,
arranged vertically between the top and bottom plates such that the
plurality of pin slices form substantially vertical pins connecting
the top and bottom plates.
3. The heat sink of claim 2, wherein the corrugated plate includes
open space around each of said protrusions to allow
flexibility.
4. The heat sink of claim 2, wherein the plurality of pin slices
layers each further comprises a plurality of curved links between
pin slices.
5. The heat sink of claim 4, wherein the curved links of adjacent
pin slice layers are arranged vertically to block coolant to
regions of lower coolant needs.
6. The heat sink of claim 4, wherein the curved links of respective
pin slice layers are omitted to increase coolant to regions of
higher coolant needs.
7. The heat sink of claim 1, further comprising a compressible
layer disposed over the top plate, configured to distribute a load
force to the top plate when the top plate is deformed.
8. The heat sink of claim 1, wherein the bottom plate is disposed
on a non-flat surface and conforms to the shape of the non-flat
surface under load and wherein the vertically arranged pin slice
layers communicate the shape of the non-flat surface to the top
plate, which deforms vertically and laterally to conform to the
non-flat surface.
9. A linked pin fin compliant heat sink, comprising: a top and
bottom plate; a plurality of pin slice layers, each comprising a
plurality of pin slices, arranged vertically between the top and
bottom plates such that the plurality of pin slices form
substantially vertical pins connecting the top and bottom plates;
and a plurality of curved links connecting laterally adjacent pin
slices in at least a pin slice layer.
10. The linked pin fin compliant heat sink of claim 9, wherein at
least one of the top and bottom plates is a corrugated plate that
includes interlocking protrusions on opposite sides of the plate
and wherein pin contacts are flexibly connected to one another by
the top and bottom plates.
11. The linked pin fin compliant heat sink of claim 10, wherein the
corrugated plate includes open space around each of said
protrusions to allow flexibility.
12. The linked pin fin compliant heat sink of claim 9, wherein the
curved links between vertically adjacent pin slice layers are
arranged to align vertically to block coolant to regions of lower
coolant needs.
13. The linked pin fin compliant heat sink of claim 9, wherein one
or more curved links of at least a respective pin slice layer are
omitted to increase coolant to regions of higher coolant needs.
14. The linked pin fin compliant heat sink of claim 9, wherein
curved links between corresponding pin slices on at least two
adjacent layers curve in different directions with respect to one
another.
15. The linked pin fin compliant heat sink of claim 9, wherein the
curved links have a thinner vertical cross-section than the pin
slice layers.
16. The linked pin fin compliant heat sink of claim 9, wherein the
plurality of curved links are arranged to create regions of higher
coolant flow and regions of lower coolant flow, such that coolant
through the heat sink follows a specified path.
17. A method for employing a heat sink, comprising: placing a pin
fin compliant heat sink on a non-flat surface, wherein the pin fin
complaint heat sink has top and bottom plates connected by a
plurality of pins arranged vertically between the top and bottom
plates; and vertically conforming the top and bottom plates to
local deviations of the non-flat surface; and laterally conforming
the top and bottom plates to an overall shape of the surface,
wherein at least either the top or bottom plate is corrugated.
18. The method of claim 17, wherein said steps of vertically and
laterally conforming the plates comprises attaching a load to a
compressible, load-distributing layer that is disposed on the top
plate of the pin fin compliant heat sink to distribute the load
across a non-flat surface of the top plate.
19. The method of claim 17, wherein at least one of the top and
bottom plates is a corrugated plate comprising a plurality of pin
contact points, each of which can displace vertically and laterally
with respect to adjacent pin contact points under load.
20. The method of claim 17, wherein the plurality of pins are
connected by curved links that compress or extend laterally between
adjacent pins under load.
Description
BACKGROUND
[0002] 1. Technical Field
[0003] The present invention relates to cooling and, more
particularly, to pin fin compliant heat sinks having enhanced
flexibility.
[0004] 2. Description of the Related Art
[0005] Compliant heat sinks provide a good heat removal solution
with low thermal resistance and substantially lower thermal
interface stresses than standard, rigid heat sinks. Compliant
heatsinks are able to conform to an irregular device surface
without damage to the heatsink or to the device. In particular, pin
fin compliant (PFC) and linked pin fin compliant (LPFC) heat sinks
have favorable compliant performance at a relatively low cost.
[0006] PFC heat sinks include an array of pins between two
compliant membranes. The PFC assembly is forced into contact with a
device to be cooled using a compression layer. Small, local
deviations from flatness are handled by PFCs with relatively low
loads, as neighboring pins can move up and down relative to one
another. Global deviations (such as a curved surface) can also be
handled with sufficient loading, but the load needs to be high
enough to bend the PFC heat sink as a whole. This puts one of the
membranes in tension, resisting the bending. In the case of LPFC
heat sinks, the links between individual pins also tend to resist
bending. As such, standard PFC and LPFC heat sinks use high degrees
of loading force when used on curved surfaces. These high loads
create a risk of damage when installing or removing the heatsink,
whether to the heatsink itself or to the device to be cooled.
SUMMARY
[0007] A heat sink includes a top and bottom plate, at least one of
which includes a plurality of pin contacts flexibly connected to
one another. The plurality of pin contacts have vertical and
lateral flexibility with respect to one another. The cooling device
further includes vertical pins connecting the top and bottom
plates.
[0008] A linked pin fin compliant heat sink includes a top and a
bottom plate. A plurality of pin slice layers, each comprising a
plurality of pin slices, is arranged vertically between the top and
bottom plates such that the plurality of pin slices form
substantially vertical pins connecting the top and bottom plates.
There is a plurality of curved links connecting laterally adjacent
pin slices in at least a pin layer.
[0009] A method for employing a heat sink includes placing a pin
fin compliant heat sink on a non-flat surface. The pin fin
complaint heat sink has top and bottom plates connected by a
plurality of pins arranged vertically between the top and bottom
plates. The top and bottom plates are vertically conformed to local
deviations of the non-flat surface. The top and bottom plates are
laterally conformed to an overall shape of the surface, wherein at
least either the top or bottom plate is corrugated.
[0010] These and other features and advantages will become apparent
from the following detailed description of illustrative embodiments
thereof, which is to be read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0011] The disclosure will provide details in the following
description of preferred embodiments with reference to the
following figures wherein:
[0012] FIG. 1 is a cross-sectional view of a pin fin compliant heat
sink in accordance with the present principles;
[0013] FIG. 2 is a cross-sectional view of a linked pin fin
compliant heat sink in accordance with the present principles;
[0014] FIG. 3 is a top-down view of a layer of pin slices and links
therebetween in accordance with the present principles;
[0015] FIG. 4 is a three-dimensional view of the top of a
corrugated plate in accordance with the present principles;
[0016] FIG. 5 is a three-dimensional view of the bottom of a
corrugated plate in accordance with the present principles;
[0017] FIG. 6 is a block/flow diagram of a method of using a pin
fin compliant heat sink in accordance with the present
principles;
[0018] FIG. 7 is a cross-sectional view of a linked pin fin
compliant heat sink on a globally curved surface in accordance with
the present principles; and
[0019] FIG. 8 is a cross-sectional view of a linked pin fin
compliant heat sink in on an irregular surface accordance with the
present principles.
DETAILED DESCRIPTION
[0020] Embodiments of the present invention provide pin fin
compliant (PFC) and linked pin fin compliant (LPFC) heat sinks with
enhanced flexibility that allow the heat sinks to be used on curved
surfaces with substantially lower loads than those needed by
conventional heat sinks. To accomplish this, the present
embodiments employ pin membranes (plates) that are corrugated
between pin contacts, which greatly reduces the effective modulus
of the membrane in tension or compression, allowing the plates to
accommodate lateral displacements as well as vertical
displacements. Lateral displacement along the top plate allows the
pins to angle away from one another, such that an overall curved
surface may be accommodated. Thus, the present embodiments provide
cooling solutions for devices and surfaces having irregular
configurations, greatly expanding the options for using such
devices in new environments.
[0021] In the context of LPFC heat sinks, the links between the
pins shown in the present embodiments may have a curved shape,
rather than a straight one. This curved shape will also have a
lower modulus in compression or tension than a straight, centered
link, allowing for much more lateral compression than straight
links would have. The curved links in the LPFC heat sink of the
present embodiments can also be formed at a higher density in areas
where lower flow is desired, while still maintaining flexibility.
This reduces or eliminates the need for separate flow blocking
elements, as the heat sink itself can be constructed to provide
specific flow pathways.
[0022] Referring now to the drawings in which like numerals
represent the same or similar elements and initially to FIG. 1, an
exemplary embodiment of a PFC cooling device is shown. A chip 104
is mounted on a substrate 102. For the present purposes, the chip
104 may be any appropriate device or circuit, and it is
specifically contemplated that the chip 104 will be an integrated
circuit package, mounted on a printed circuit board substrate 102.
Although the chip 104 is shown as being flat for ease of
illustration, it should be recognized that the top surface of the
chip 104 may be uneven or curved. It is assumed for the present
purposes that the chip 104 generates heat during operation, which
necessitates some form of cooling, though the heat could also be
generated within or behind the substrate 102.
[0023] A cooling device 106 is mounted on the chip 104, either
directly or with some appropriate thermally conductive medium such
as a thermal paste. The chip 104 has some irregularity in its
surface, including one or more of local irregularities, such as a
feature that extends from the plane of the surface. The chip 104
may also include global irregularities, such as an overall curve.
According to the present principles, the cooling device 106
conforms to the surface of the chip 104 when pressure is applied.
Heat passes to the cooling device 106 from the chip 104 and is
dissipated by pins/fins 108. In the present example, the cooling
device is an enclosure that channels air or some other coolant past
pins 108, transporting the dissipated heat away from the chip 104.
The coolant in question may be any appropriate fluid having
suitable mechanical and thermal properties, including a high heat
capacity and a low viscosity. In one specific embodiment, it is
contemplated that water may be used as a coolant, but alternative
coolants such as air, oil, or a liquid metal such as mercury,
gallium or a gallium alloy such as with tin or indium.
[0024] A load 112 is applied to the cooling device 106. The load
112 is specifically contemplated as being a force provided by,
e.g., a clamp, weight, or some other device that holds the cooling
device 106 tightly onto the chip 104. The pressure generated by the
load 112 provides good thermal contact between the cooling device
106 and the chip 104. A thermal paste or other thermally conductive
compound (not shown) may be interposed between the cooling device
106 and the chip 104 to maximize thermal contact and heat flow
between the two.
[0025] As noted above, the chip's surface may be uneven or curved.
By conforming to the uneven surface of the chip 104, the cooling
device 106 will have some corresponding deformation on its top
surface as the pins 108 translate the deformation from the chip's
surface. As such, an elastomer or spring array 110 is used between
the load 112 and the cooling device 106 to transfer the force of
the load 112 evenly across the cooling device 106. The elastomer
110 can be, for example, a rubber sheet which is disposed between
the surface of load 112 and the top lid of the heat sink 106. The
elastomer 110 may alternatively be formed as the top lid of the
heat sink 106 itself, though care should be taken to ensure that
coolant does not leak under deformation. Because the surfaces of
the heat sink 106 may be corrugated, there may be openings in the
heat sink 106 that the elastomer 110 should block. The elastomer
layer 110 could also be replaced with an array of springs which
provide a large number of distributed load points across the top of
the PFC or LPFC heat sink 106.
[0026] Referring now to FIG. 2, a detailed view of a portion of the
cooling device 106 is shown in cross-section. This view shows an
LPFC embodiment that has corrugated plates 202 connected by stacked
pin slices 204. The individual slices 204 are laterally linked to
one another by flexible connecting elements 206. The corrugated
lids 202 allow relative vertical displacement of the stacks of pin
slices 204 as well as lateral displacement. The connecting elements
206 are curved and flexible, allowing compression and extension
between pin stacks 204 during lateral displacement. In the case of
a PFC heat sink, the connecting elements 206 may be omitted. In any
case, connecting elements 206 located in vertically neighboring
layers should not be bonded to one another to maintain flexibility.
As such, a gap is visible in FIG. 2 between the connecting elements
206 of adjacent levels. This gap allows coolant flow through the
heat sink 106 as well.
[0027] It is specifically contemplated that the pin slices 204 may
be formed from copper or a copper alloy, but it should be
understood that any material with good heat conducting properties
may be used instead. It is further contemplated that the connecting
elements 206 may be formed from the same material as the pin slices
204 and that the slices 204 and the connecting elements 206 may be
formed by etching sheets of material. The layers may also be formed
using punch dies, by electroplating on a pattern, or by any other
appropriate fabrication method. The individual layers may be simply
arranged above one another, or the layers may have an adhesive or
other type of bond between the slices 204. Bonding the slices 204
provides strength and improves heat conduction between adjacent
slices 204, but may decrease flexibility in some cases.
[0028] Referring now to FIG. 3, a top-down view of a layer of pin
slices 204 is shown. The layer is formed from pin slices 204,
connected by connecting links 206. As shown, the connecting links
206 are curved to allow flexibility. The flexibility of the
connections between laterally adjacent stacks of pin slices 204 may
be increased by removing or thinning the links 206 using, for
example, an etching process or a mechanical separation with an
edged die. This allows precise control of the structure of the
layers with respect to the connections between slices 204.
[0029] Although the links 206 are shown as being arranged in a
regular pattern, the flow rate of coolant through the device 106
may also be controlled by selectively adding or removing links.
Additionally, the links in in adjacent layers may be arranged to
match or differ in the direction of their curve. For example, a
stack of links that curve in the same direction will limit coolant
flow more than if those links alternate in curve direction,
allowing wider gaps between them. Links near the edge of the
cooling device 106 that connect the same pair of slices 204 in
adjacent layers serve to reduce flow in an inactive area of the
chip 104. To allow flow to an area, the links may be arranged to
curve in different directions, to connect to different slices 204,
or to be entirely absent in an area of high flow--bearing in mind
that each slice 204 may be connected to at least one neighboring
slice 204 to maintain structural integrity. In this manner, the
cooling device 106 may be designed to have a three-dimensional
network of connections 206, the density of which along any given
plane optimizes coolant flow around the chip, providing additional
flow to areas that need additional cooling and reducing flow to
areas that need less.
[0030] The use of curved links 206 provides additional options for
customizing the rate of cooling. For example, consider two stacked
layers. If two adjacent pin slices 204 in a given layer are
connected by a link 206 that curves in a first direction, the
corresponding pin slices 204 in the adjacent layer may be connected
by a link 206 that curves in a second direction. This allows more
coolant flow than two stacked links 206 that curve in the same
direction. Additionally, although links 206 are shown using a
single, uniform curvature, the shapes of the links 206 may be
varied and may be non-uniform. For example, links in areas where
high flexibility is needed may have multiple curves or may have
curves that are more pronounced, allowing for additional lateral
motion of the cooling device 106. Links 206 in areas where less
flexibility is needed or desired may have shapes that are less
flexible, lending additional strength to the cooling device 106.
The links 206 are essentially springs, and the spring constant of
each link 206 may be controlled as appropriate.
[0031] Referring now to FIG. 4, a three-dimensional view of a "top"
of one embodiment for the lids 202 of the cooling device 106 is
shown. The lid 202 includes a set of pin contacts 402 that align
with the pin slices 204 of the adjacent layer. The pin contacts 402
are flexibly connected to a lid body 404. As shown, gaps between
the pin contacts 402 and the lid body 404 provide flexibility that
allows the lid contacts 402 to shift laterally with respect to one
another, as well as transversely to the body 404.
[0032] Referring now to FIG. 5, a three-dimensional view of a
"bottom" of the lids 202 of the cooling device 106 is shown. From
this angle, a set of cylindrical protrusions 502 are visible which
are shown in cutaway to reveal a flexible ring 504 around the pin
contacts 402. It is specifically contemplated that the lids will be
made of copper, with the pictured structures created by an etching
process, but it should be understood that the described embodiments
may be formed using any appropriately conductive and flexible
material and by any appropriate process, including, e.g., stamping
and molding.
[0033] These embodiments of the lids 202 allow the individual pins
to move vertically to conform to local deviations on the chip 104,
but they also allow larger-scale deviations, such that the entire
lid may flex to conform to a curved surface. In this manner, the
PFC cooling device 106 may be used to provide cooling to a wide
variety of surfaces that were not previously feasible. Although
only two examples are shown herein, it is contemplated that those
having ordinary skill in the art would be able to apply the present
principles to create other shapes of corrugated lid in accordance
with the present principles.
[0034] In one exemplary embodiment, the thickness of the lids is
about 0.25 mm, with pin spacing in the range of 1.0 mm. These
dimensions can be scaled up or down depending on the coolant type
and the device to be cooled. These dimensions are provided for
typical scenarios using semiconductor devices and liquid coolant,
but for example a coolant having a lower viscosity (such as air)
could have a smaller pin spacing without sacrificing coolant flow.
It is similarly contemplated that pin diameters may be about 0.5
mm. Pin diameter for a given pin spacing trades off thermal
effectiveness with coolant pressure drop, as larger pins have a
higher surface area but block more of the coolant flow.
[0035] In an alternative embodiment of a corrugated lid, a complete
or partially complete stack of layers 204, including the top and/or
bottom lid 202, may be pressed together. This creates a `W-shaped
connection between neighboring pins, rather than the flat
connection created by a flat plate, as the once-flat membrane/plate
is forced inward between the pins.
[0036] Referring now to FIG. 6, a method of applying a cooling
device to a surface is shown. Block 602 places a PFC or LPFC
cooling device 106 onto a curved surface. In the present
embodiments, the surface may include chip 104 or any other curved
surface that needs cooling. It should be recognized that the
"curved surface" discussed herein need not have a smooth curve, but
may have a stepped contour or any arbitrary shape. After the
cooling device 106 is placed on the curved surface, block 604
applies a load 112 to the cooling device 106 that causes it to
conform to the contours of the surface. To accomplish this, the
load 112 itself should have some ability to conform to the contours
as well, or should use an elastic or compressible layer 110 (e.g.,
an elastomer or distributed spring) to translate the flat force of
the load 112 to the curved contour of the top surface of the
cooling device 106. Block 606 then causes the cooling device 106 to
conform to the curved surface, where the corrugated lids 202 and
the curved links 206 allow both vertical displacement as well as
lateral displacement.
[0037] Referring now to FIG. 7, an embodiment is shown with a LPFC
heatsink being applied to a curved surface 104. The corrugated
plates shift vertically as well as horizontally with respect to one
another, allowing them to accommodate the overall curve of the
surface 104. In particular, the pins 702 in the center are
relatively parallel with respect to one another, being over a flat
portion of the surface 702, while the pins 704 at the ends are
tilted to accommodate the curve. Also shown is the elastic layer
706, which conforms to the top surface of the top corrugated plate
as a down pressure is applied. The elastic properties of the layer
706 help to distribute the downward force across the curved
surface, which a rigid load would be unable to do. While less force
will be applied to the outer pins 704 than to the inner pins 702,
the corrugated configuration of the plates allows the entire
heatsink to assume the shape of the surface 104 with less extreme
pressures.
[0038] While the curved surface 104 is shown as having a relatively
uniform shape, it should be understood that the surface 104 can
have any shape. In particular, it should be recognized that the
surface 104 can have local irregularities as well as global
curvature, and that the pins will accommodate these irregularities
primarily with vertical displacement.
[0039] Referring now to FIG. 8, an illustration of a curved surface
802 with a local irregularity is shown. In this instance, a single
pin 804 displaces vertically to accommodate the irregularity in the
surface 802. As above, the elastic layer 706 conforms to the top
surface of the corrugated plate to provide downward pressure on the
displaced pin 804 as well as on the remainder of the plate, thereby
providing good thermal contact for the entire heat sink. While the
figure shows a section moving in its entirety, it should be noted
that both the top and bottom plates are essentially contiguous,
forming a seal for the coolant flowing between them.
[0040] Thus, by providing the ability to deform vertically and
horizontally, the present embodiments provide compliant heatsinks
that can accommodate any surface geometry without applying a large
force. This allows the present embodiments to be used on relatively
delicate, irregularly-shaped surfaces, where a large amount of
force might otherwise damage the device to be cooled.
[0041] The flowchart and block diagrams in the Figures illustrate
the functionality, and operation of possible implementations of
systems and methods according to various embodiments of the present
invention. It should also be noted that, in some alternative
implementations, the functions noted in the blocks may occur out of
the order noted in the figures. For example, two blocks shown in
succession may, in fact, be executed substantially concurrently, or
the blocks may sometimes be executed in the reverse order,
depending upon the functionality involved.
[0042] Reference in the specification to "one embodiment" or "an
embodiment" of the present principles, as well as other variations
thereof, means that a particular feature, structure,
characteristic, and so forth described in connection with the
embodiment is included in at least one embodiment of the present
principles. Thus, the appearances of the phrase "in one embodiment"
or "in an embodiment", as well any other variations, appearing in
various places throughout the specification are not necessarily all
referring to the same embodiment.
[0043] It is to be appreciated that the use of any of the following
"/", "and/or", and "at least one of", for example, in the cases of
"A/B", "A and/or B" and "at least one of A and B", is intended to
encompass the selection of the first listed option (A) only, or the
selection of the second listed option (B) only, or the selection of
both options (A and B). As a further example, in the cases of "A,
B, and/or C" and "at least one of A, B, and C", such phrasing is
intended to encompass the selection of the first listed option (A)
only, or the selection of the second listed option (B) only, or the
selection of the third listed option (C) only, or the selection of
the first and the second listed options (A and B) only, or the
selection of the first and third listed options (A and C) only, or
the selection of the second and third listed options (B and C)
only, or the selection of all three options (A and B and C). This
may be extended, as readily apparent by one of ordinary skill in
this and related arts, for as many items listed.
[0044] Having described preferred embodiments of a pin fin
compliant heat sink with enhanced flexibility and methods for using
the same (which are intended to be illustrative and not limiting),
it is noted that modifications and variations can be made by
persons skilled in the art in light of the above teachings. It is
therefore to be understood that changes may be made in the
particular embodiments disclosed which are within the scope of the
invention as outlined by the appended claims. Having thus described
aspects of the invention, with the details and particularity
required by the patent laws, what is claimed and desired protected
by Letters Patent is set forth in the appended claims.
* * * * *